You need to use Stoichiometry
C. Its density is less than water
This is why. The denser the object is the farther it sinks. Since crystallized ice floats it is less dense than the surrounding liquid.
Explanation:
Relation between molarity and molar mass is as follows.
Molarity = 
It is given that mass is 1 mg/ml which is also equal to
g.
Molecular mass = 58 Da = 58 g/mol
Volume = 1 ml
Therefore, calculate molarity as follows.
Molarity = 
=
= 0.0172 molar
It is known that 1 molar equals 1000 millimolar.
So, 0.0172 molar = 
= 17.2 millimolar
Thus, we can conclude that the concentration of given solution is 17.2 millimolar.
Answer: B is a gas because its volume is less than the volume of the containers.
Explanation: hope this help bye